More than two years after an outside contractor was hired to run one of the city's most venerable schools, D.C. officials said Tuesday that Dunbar High remains plagued by a litany of troubles: Nearly half the senior class is not on track to graduate, more than 100 students are taking courses they've already passed and the campus is growing increasingly unsafe.

Interim Schools Chancellor Kaya Henderson made those findings and others public to justify her decision last week to oust Friends of Bedford, the New York-based contractor that former chancellor Michelle A. Rhee retained to turn around the 822-student school.

"In general, the building seems to be in turmoil at all times," Henderson wrote in a termination letter made public this week. "Well after the school day begins, many students are wandering around the building, strolling to class with absolutely no sense of urgency."

While problems at Dunbar have festered for months, the situation has turned into an early test of how Henderson and Mayor-elect Vincent C. Gray (D) will respond to school reform efforts that appear to go awry. On Tuesday, after a week of news describing disorder and disarray at the school several months into the academic year, Gray and Henderson joined Mayor Adrian M. Fenty (D) in an attempt to turn the page. They gathered at the school on New Jersey Avenue NW to unveil the design for a long-planned $100 million new Dunbar to open in fall 2013.

Named for the renowned African American poet Paul Laurence Dunbar and located less than two miles from the U.S. Capitol, Dunbar was the nation's first municipally funded public high school for blacks. But it has spent years in decline. By the time Rhee hired Bedford, the school had failed for five consecutive years to make adequate yearly progress in test scores under the federal No Child Left Behind Law.

The contractor was given broad latitude in hiring, scheduling and curriculum even though Dunbar remained subject to D.C. laws and labor contracts. But Henderson said the school's record, as well as classroom observations and complaints from teachers and parents, led her to conclude that the environment at Dunbar had "deteriorated significantly."

George Leonard, chief executive of Bedford, which is still responsible for overseeing the city's Coolidge High, said he disagreed with Henderson's views on Dunbar but would back her decision. "I'm going to support everything she's doing," Leonard said. "Her position as [interim] chancellor is difficult enough as it is. I want to help."

Some of the data show Dunbar's troubles are comparable to those in the school system's eight other neighborhood high schools with open enrollment. Although 45 percent of Dunbar's seniors are designated "potential non-graduates" - meaning they would not get a diploma even if they pass every course for which they are currently scheduled - the citywide average for the open-enrollment high schools is 39 percent.

Dunbar has had 22 security incidents this fall deemed "serious," meaning they involved fighting, assault or incidents with weapons. That places the school just slightly above Woodson and Ballou high schools, both with 19. Police arrested six Dunbar students last month and charged them with raping a female student in a stairwell. The charges were later dropped, but the school community was shaken.

Parents and teachers have complained to Henderson and Gray about Bedford's management approach. They said Leonard made an array of promises about new equipment and improved programs that have not come to pass since the firm assumed control of the school in 2009. Parents also accused Bedford of being uncommunicative, cutting them out of decisions.

Henderson, who was a top deputy under Rhee, said that because Bedford was given autonomy and a premium of about $1.2 million in the past year above usual funding levels, she expected more progress. Some of those funds also paid for the contractor to run Coolidge.

"I made the decision to change the Dunbar leadership and provide additional supports to ensure that Dunbar becomes a place where teachers can teach and children can learn," Henderson said.

Bedford officials said that because they no longer had access to pertinent records, it was difficult to respond to the city's findings in detail. In general, they said that data about graduation and student schedules tended to be a snapshot that often changed quickly. They disputed the District's finding that about 45 percent of Dunbar seniors are in jeopardy of not graduating.

Bevon Thompson, Bedford's chief financial officer and lead data analyst, said that the estimate of those at risk "does not seem correct" and that at a meeting with school staff this fall he recalled that about 80 percent of seniors were on track to graduate.

Thompson also questioned the District's finding that 109 students are mistakenly enrolled in courses they've already passed. He said it might reflect a stream of students who transferred into the school after the semester began. Typically, he said, it takes time for new student records - especially those from charter schools - to show up in the public school database. Students may initially be assigned to courses they've already taken, Thompson said.

Bedford's experience underscores the extreme difficulty in turning around chronically failing schools. Friendship Public Charter Schools, a group Rhee also hired in 2008, operates Anacostia Senior High School. This fall, Scholar Academies, a Philadelphia charter operator, was placed in charge of Stanton Elementary.

But studies find that the success rate for such managerial change is low. And community leaders say Bedford's experience at Dunbar suggests that sustainable reform must come from the ground up, beginning with parents, teachers and other stakeholders.

"The sense that someone can come in and 'fix' us is the wrong methodology," said Cathy Reilly, director of the Senior High Alliance of Parents, Principals and Educators, which supports public high schools. "This model may not be the model for us."